International Journal of Molecular Sciences · 9 authors, 6 centres
This summary was generated by AI from a single paper. It has not been reviewed by a clinician and is not clinical advice. Verify against the source before acting on it.
This study in a rat model of metabolic syndrome (MetS) found that pre-treatment with the PPARα agonist clofibrate reduced cardiac inflammation, fibrosis, and apoptosis caused by ischemia/reperfusion (I/R) injury. Clofibrate also decreased the compensatory upregulation of atrial natriuretic peptide (ANP) and its receptor (ANPr) in the heart. These findings suggest that PPARα activation may be a therapeutic strategy to protect the heart from I/R damage in patients with metabolic syndrome.
**Background:** Metabolic syndrome (MetS) is a cluster of risk factors—hypertension, obesity, insulin resistance, and dyslipidemia—that doubles the risk of coronary artery disease and heart failure. Myocardial ischemia/reperfusion (I/R) injury triggers a complex inflammatory response involving cytokines (TNF-α, IL-1β, IL-6), matrix remodeling via metalloproteinases (MMP-2), fibrosis, and apoptosis. Natriuretic peptides (NPs) like ANP and BNP are cardiac hormones with cardioprotective effects mediated through the ANP receptor (ANPr), but their role in I/R injury remains controversial. Peroxisome proliferator-activated receptor α (PPARα) agonists, such as fibrates, have pleiotropic cardioprotective effects including anti-inflammatory and anti-remodeling actions, but their effect on NP signaling in I/R injury is not well understood. This study tested the hypothesis that clofibrate, a PPARα agonist, protects the heart from I/R injury in MetS rats by modulating inflammation, remodeling, apoptosis, and the ANP/ANPr system.
**Methods:** Male Wistar rats (25 days old) were divided into control (tap water) and MetS (30% sucrose in drinking water for 24 weeks) groups. Both groups were further subdivided to receive vehicle or clofibrate (100 mg/kg/day i.p.) for 7 days. Animals then underwent either sham surgery or I/R (30 min LAD ligation, 60 min reperfusion). Left ventricle tissue was analyzed for: pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) by ELISA; myocardial fibrosis by picrosirius red staining (collagen volume fraction, CVF); MMP-2 expression by Western blot; ANP and ANPr expression by immunofluorescence and immunogold electron microscopy; NT-proBNP by ELISA; and apoptosis by TUNEL assay. Statistical analysis used one-way ANOVA with Tukey's post-hoc test or Kruskal-Wallis as appropriate.
**Key Results:** MetS rats were hypertensive, dyslipidemic (high triglycerides, low HDL), centrally obese, and insulin resistant. Clofibrate reduced body weight, central obesity, triglycerides, and improved insulin sensitivity in MetS rats. Pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) were approximately three times higher in MetS sham rats vs. control sham. I/R further increased these cytokines, and clofibrate pre-treatment prevented this increase by approximately 45% for IL-1β, 30% for IL-6, and 55% for TNF-α. MetS hearts showed more infiltrated cells and higher collagen deposition (CVF) than controls, which was exacerbated by I/R and reduced by clofibrate. MMP-2 expression was significantly higher in MetS hearts (sham and I/R) vs. controls, and clofibrate significantly decreased MMP-2 in both Ct and MetS groups. ANP and ANPr immunofluorescence was markedly increased in MetS-V-IR rats compared to MetS sham, and clofibrate pre-treatment significantly decreased this signal. Immunogold electron microscopy confirmed greater ANP and ANPr presence in mitochondria and fibers of MetS hearts, which was reduced by clofibrate. NT-proBNP concentrations were not statistically different among groups. Apoptosis (TUNEL-positive cells) was significantly increased in MetS sham vs. control sham, and clofibrate prevented apoptosis in the MetS group.
**Clinical Implications:** This study provides preclinical evidence that PPARα activation with clofibrate reduces cardiac inflammation, fibrosis, MMP-2 expression, and apoptosis in a MetS rat model of I/R injury. The finding that clofibrate also downregulates the compensatory increase in ANP/ANPr expression suggests a novel mechanism linking PPARα signaling to the natriuretic peptide system. These results support the potential repurposing of fibrates as cardioprotective agents in patients with metabolic syndrome who are at high risk for myocardial infarction and reperfusion injury. However, these findings are from an animal model and require validation in human clinical studies. The lack of significant NT-proBNP differences among groups may reflect the measurement of the inactive N-terminal fragment in tissue rather than circulation, and further studies are needed to clarify the role of BNP in this context.